From the DE-PS 42 44 595 a process for the continuous production of beer is known, where starch-containing raw materials are mashed with water, and the mash is continuously supplied to at least one reactor. Through indirect heat exchange the temperature of the mash before addition to the individual reactors is gradually raised to a final temperature of 75 to 85.degree. C. The dwell time in the reactors is 30 to 90 minutes, and the mash in the individual reactors is kept at a defined temperature level. The grains are continuously separated from the mash in a decanter and are subsequently leached out with the brewing water in a two-stage decanter. The hot wort is mixed with hop or hop extract and is continuously supplied to a flow reactor and heated to a temperature of 105 to 140.degree. C. During the passage through the reactor for 2 to 60 minutes the wort is maintained at this temperature and a pressure of 1.2 to 3.6 bar. The pressurized wort is subjected to a flash evaporation, continuously liberated from the turbid matter in a separator and then cooled to the fermentation temperature in a heat exchanger. The cooled wort with an oxygen content of 0.5 to 3.0 mg O.sub.2 per liter is continuously supplied to at least one fermenter designed as a loop reactor operating at a temperature of 6 to 25.degree. C. and a pressure of 1.5 to 2 bar, in which the wort has an average dwell time of 10 to 40 hours and is continuously circulated. There is a biocatalyst containing a biologically active yeast, where during the fermentation, liquid medium is continuously withdrawn from the fermenter and is centrifuged for removing the free yeast cells contained therein. The yeast-free liquid medium is heated to 60 to 90.degree. C. for 0.5 to 30 minutes and is subsequently cooled by expansion, where a partial stream is recirculated to the fermenter, and the second partial stream is discharged as finished product after a filtration.
In the execution of this process it has turned out in some cases that the taste quality of the beer has yet to be improved, which is due to the fact that the separation of the diacetyl formed through thermal conversion of a-acetolactate can not always be achieved almost quantitatively by means of the heat treatment, expansion and partial recirculation of the finished product to the fermentation provided in accordance with the known process. Thus, the object of the present invention is the improvement of the taste quality of continuously produced beers, in particular by lowering their diacetyl content.
A taste improvement through conversion of the byproducts formed during the primary fermentation is usually effected during the storage of the young beer referred to as maturation, which is performed for some weeks at low temperatures. Such storage requires corresponding storage rooms and stock-keeping. Therefore, tests on the fast maturation of beer have already been carried out. From the DE-PS 41 37 474 a process is known for the continuous fast maturation of beer through further conversion of the wort treated in the primary fermentation step with yeast on a carrier. The conversion is performed at an elevated pressure in a fluidized-bed reactor with yeast immobilized on macroporous granulate having a porosity of 40 to 65% with pore sizes of 60 to 300 .mu.m and a particle size.ltoreq.3 mm. As carrier macroporous glass granulate with a particle size of 1 to 2 mm is used and temperatures of 2 to 10.degree. C. as well as dwell times of 5 to 15 hours are employed. Furthermore, from the DE-PS 24 29 574 a process is known for the continuous production of beer comprising a fermentation of the beer wort while flowing through a fermenter. The wort is passed through a fermentation tower containing yeast which is disposed on a carrier consisting of diatoms or granular polyvinylchloride. The young beer coming from the fermentation tower is passed through a storage tower, which corresponding to the fermentation tower has a yeast-containing carrier, and where the beer coming from the storage tower is passed through a treatment tower which has proteases on a carrier of organic polymers, bricks, silica, glass, sand, silica-based compounds or clay-containing substances.